linux-kernel - Re: [PATCH v14 05/23] x86/virt/tdx: Handle SEAMCALL no entropy error in common code

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Message-ID: <736a6745-3ba7-4a0e-a00c-bb36fa1cc51c@linux.intel.com>
Date:   Tue, 17 Oct 2023 06:34:36 -0700
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Kai Huang <kai.huang@...el.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     x86@...nel.org, dave.hansen@...el.com,
        kirill.shutemov@...ux.intel.com, peterz@...radead.org,
        tony.luck@...el.com, tglx@...utronix.de, bp@...en8.de,
        mingo@...hat.com, hpa@...or.com, seanjc@...gle.com,
        pbonzini@...hat.com, rafael@...nel.org, david@...hat.com,
        dan.j.williams@...el.com, len.brown@...el.com, ak@...ux.intel.com,
        isaku.yamahata@...el.com, ying.huang@...el.com, chao.gao@...el.com,
        nik.borisov@...e.com, bagasdotme@...il.com, sagis@...gle.com,
        imammedo@...hat.com
Subject: Re: [PATCH v14 05/23] x86/virt/tdx: Handle SEAMCALL no entropy error
 in common code



On 10/17/2023 3:14 AM, Kai Huang wrote:
> Some SEAMCALLs use the RDRAND hardware and can fail for the same reasons
> as RDRAND.  Use the kernel RDRAND retry logic for them.
> 
> There are three __seamcall*() variants.  Do the SEAMCALL retry in common
> code and add a wrapper for each of them.
> 
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> Reviewed-by: Kirill A. Shutemov <kirll.shutemov@...ux.intel.com>
> ---
> 
> v13 -> v14:
>  - Use real function sc_retry() instead of using macros. (Dave)
>  - Added Kirill's tag.
> 
> v12 -> v13:
>  - New implementation due to TDCALL assembly series.
> ---

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com

>  arch/x86/include/asm/tdx.h | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index a252328734c7..d624aa25aab0 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -24,6 +24,11 @@
>  #define TDX_SEAMCALL_GP			(TDX_SW_ERROR | X86_TRAP_GP)
>  #define TDX_SEAMCALL_UD			(TDX_SW_ERROR | X86_TRAP_UD)
>  
> +/*
> + * TDX module SEAMCALL leaf function error codes
> + */
> +#define TDX_RND_NO_ENTROPY	0x8000020300000000ULL
> +
>  #ifndef __ASSEMBLY__
>  
>  /*
> @@ -82,6 +87,27 @@ u64 __seamcall(u64 fn, struct tdx_module_args *args);
>  u64 __seamcall_ret(u64 fn, struct tdx_module_args *args);
>  u64 __seamcall_saved_ret(u64 fn, struct tdx_module_args *args);
>  
> +#include <asm/archrandom.h>
> +
> +typedef u64 (*sc_func_t)(u64 fn, struct tdx_module_args *args);
> +
> +static inline u64 sc_retry(sc_func_t func, u64 fn,
> +			   struct tdx_module_args *args)
> +{
> +	int retry = RDRAND_RETRY_LOOPS;
> +	u64 ret;
> +
> +	do {
> +		ret = func(fn, args);
> +	} while (ret == TDX_RND_NO_ENTROPY && --retry);
> +
> +	return ret;
> +}
> +
> +#define seamcall(_fn, _args)		sc_retry(__seamcall, (_fn), (_args))
> +#define seamcall_ret(_fn, _args)	sc_retry(__seamcall_ret, (_fn), (_args))
> +#define seamcall_saved_ret(_fn, _args)	sc_retry(__seamcall_saved_ret, (_fn), (_args))
> +
>  bool platform_tdx_enabled(void);
>  #else
>  static inline bool platform_tdx_enabled(void) { return false; }

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer